What is Dissolved Organic Matter (DOM)?
Graphic from Stedmon and Nelson (2015)
The carbon fraction (DOC) is the major part of the bioreactive fraction of the dynamic carbon pool on Earth.
From Y. T. Prairie (2008)
Important driver of ecosystem functionning:
Many processes of transformation and production acting simultaneously.
In recent decades, climate changes, eutrophication and changes in land use have contributed to increased inputs of colored terrestrial DOM in aquatic ecosystems (Roulet and Moore 2006; Haaland et al. 2010; Massicotte et al. 2013; Weyhenmeyer, Prairie, and Tranvik 2014).
This has important consequences since the transformation of even a small fraction of the DOM pool can potentially have large impacts on ecosystem functioning (Y. T. Prairie 2008).
Increases in CO2 emissions (Lapierre et al. 2013) and reduction in primary production due to light shading (Thrane, Hessen, and Andersen 2014; Seekell et al. 2015) have already been documented as consequences of increases in terrestrial DOM at local and regional scales.
Graphic from Seekell et al. (2015)
CDOM absorption can be used to characterize the DOM pool.
Use all available data to explore the dynamic of DOM around the world.
Submitted to Limnology & Oceanography
Gather and analyze all available data containing both DOC and CDOM measurements.
World map showing the spatial distribution of the observations extracted from the literature (n = 13 032 on ~70 studies conducted between 1990 and 2015).
Barplot showing the number of unique observations for (A) principal regions and (B) ecosystems.
Absorption of CDOM is reported at different wavelengths.
Results of the linear regressions between \(a_{CDOM}(350)\) and \(a_{CDOM}(\lambda)\).
We decided to choose 350 nm has the reference wavelength.
Determination coefficient (R2) showing the goodness of the linear fit between DOC and absorption coefficients measured at different wavelengths.
Strong relationship at global scale.
(A) Global relationship between absorption at 350 nm a CDOM (350) and dissolved organic carbon. (B) Barplot showing the determination coefficient (R2) of the linear relationships between a CDOM (350) and DOC by ecosystems. The dashed horizontal line represents the average of R2.
Relationship highly variable among ecosystems.
Strong bi-linear pattern along the spatial gradient (inland water \(\rightarrow\) open ocean).
Averaged SUVA254 calculated using observations from river and ocean ecosystems as a function of the distance to the closest shoreline. Positive distances represent inland samples (rivers) whereas negative distances represent oceanic samples.
Over a distance of 4000 km, a piecewise linear regression showed that the observed decrease of SUVA occurred more than 1300 times faster in freshwater ecosystems compared to marine water ecosystems, suggesting that degradation processes preferentially CDOM over DOC.
Active processing of DOM around continents.
World map showing the 370 km buffer zone identified by the segmentation analysis.
More than just conservative mixing.
Segmentation analysis performed on the linear relationship between SUVA254 and salinity.
Loiselle et al. (2009) developed an approach to characterize the absorption characteristics of CDOM. This method, based on the derivative signal of the absorption signal, allows to determine the wavelength intervals where there are changes in the spectral slope.
Spectral slope curve (Sλ) calculated on averaged absorption spectra on freshwater and marine ecosystems using a 21 nm wavelength interval. R2 for the calculated fit is indicated by color for each point on the spectrum.
Collecting the dataset used in this study has shown that there are shortcomings in the CDOM community in making the scientific data openly available.
While we fully acknowledge the considerable amount of work and funds used to acquire the data, it is vital to emphasize the importance of making spectral data available in open access databases so that the data collected can continue to contribute to progress in the field.
One of the first steps to make the data available (after a reasonable period of exclusive use) would be to use the existing data portals such as:
Pangaea (https://www.pangaea.de/)
DRYAD (http://datadryad.org/)
Make your data open and reproductible!
I can’t find the data anymore…
Haaland, S., D. Hongve, H. Laudon, G. Riise, and R. D. Vogt. 2010. “Quantifying the Drivers of the Increasing Colored Organic Matter in Boreal Surface Waters.” Environmental Science & Technology 44 (8): 2975–80. doi:10.1021/es903179j.
Lapierre, Jean-François, François Guillemette, Martin Berggren, and Paul a del Giorgio. 2013. “Increases in terrestrially derived carbon stimulate organic carbon processing and CO2 emissions in boreal aquatic ecosystems.” Nature Communications 4 (December): 2972. doi:10.1038/ncomms3972.
Loiselle, Steven A., Luca Bracchini, Arduino M. Dattilo, Maso Ricci, Antonio Tognazzi, Andres Cézar, and Claudio Rossi. 2009. “The optical characterization of chromophoric dissolved organic matter using wavelength distribution of absorption spectral slopes.” Limnology and Oceanography 54 (2): 590–97. doi:10.4319/lo.2009.54.2.0590.
Massicotte, Philippe, Denis Gratton, Jean-Jacques Frenette, and Ali A. Assani. 2013. “Spatial and temporal evolution of the St. Lawrence River spectral profile: A 25-year case study using Landsat 5 and 7 imagery.” Remote Sensing of Environment 136 (September). Elsevier B.V.: 433–41. doi:10.1016/j.rse.2013.05.028.
Prairie, Yves T. 2008. “Carbocentric limnology: looking back, looking forward.” Canadian Journal of Fisheries and Aquatic Sciences 65 (3): 543–48. doi:10.1139/f08-011.
Roulet, Nigel, and Tim R Moore. 2006. “Environmental chemistry: Browning the waters.” Nature 444 (7117): 283–84. doi:10.1038/444283a.
Seekell, David a., Jean-François Lapierre, Jenny Ask, Ann-Kristin Bergström, Anne Deininger, Patricia Rodríguez, and Jan Karlsson. 2015. “The influence of dissolved organic carbon on primary production in northern lakes.” Limnology and Oceanography 60 (4): 1276–85. doi:10.1002/lno.10096.
Seitzinger, S P, H Hartnett, R Lauck, M Mazurek, T Minegishi, G Spyres, and R Styles. 2005. “Molecular-level chemical characterization and bioavailability of dissolved organic matter in stream water using electrospray-ionization mass spectrometry.” Limnology and Oceanography 50 (1). Seitzinger, SP Rutgers State Univ, Inst Marine & Coastal Sci, 71 Dudley Rd, New Brunswick, NJ 08901 USA Rutgers State Univ, Inst Marine & Coastal Sci, New Brunswick, NJ 08901 USA: 1–12. doi:10.4319/lo.2005.50.1.0001.
Stedmon, Colin A., and Norman B. Nelson. 2015. “The Optical Properties of DOM in the Ocean.” In Biogeochemistry of Marine Dissolved Organic Matter, edited by Dennis A. Hansell and Craig A. Carlson, Academic P, 481–508. Burlington: Elsevier. doi:10.1016/B978-0-12-405940-5.00010-8.
Thrane, Jan-Erik, Dag O. Hessen, and Tom Andersen. 2014. “The Absorption of Light in Lakes: Negative Impact of Dissolved Organic Carbon on Primary Productivity.” Ecosystems 17 (6): 1040–52. doi:10.1007/s10021-014-9776-2.
Weyhenmeyer, Gesa A., Yves T. Prairie, and Lars J. Tranvik. 2014. “Browning of Boreal Freshwaters Coupled to Carbon-Iron Interactions along the Aquatic Continuum.” Edited by Tomoya Iwata. PLoS ONE 9 (2): e88104. doi:10.1371/journal.pone.0088104.